Integrally molded bearing block assembly

ABSTRACT

The assembly of a support and a slide carried by the support for translational movement relative thereto in which the support defines a slide opening having opposed end edges and opposed side edges, the side edges diverging from each other proceeding from one of said end edges toward the other of said end edges and defining guide means also so diverging, the slide having a pair of side edge formations complementing the guide formations and being of a length less than the distance between the end edges of the slide opening so that upon movement away from the one end edge of the slide opening, a sliding clearance develops between the edge formations of the slide and the guide formations in the opening. The assembly is formed by a two shot molding process in which the plate assembly is first formed using a plastic material having a relatively high melting temperature, enclosing the preformed support in a mold to define a cavity for the slide, such cavity including the side edges of the slide opening in the support, and then injecting a second plastic material of relatively low melting temperatures into the mold cavity to form the slide. The assembly is particularly useful in providing end supporting subassemblies in spread roller assemblies used for processing exposed film units in instant cameras. Both the support and the slide are preferably formed glass filled plastic materials for meeting required strength and minimal molding shrinkage.

This is a division of application Ser. No. 285,976, filed July 23, 1981now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a method for molding multi-part assemblies andto products formed by such methods. More particularly, it concerns amethod for molding support assemblies for spread rollers of photographiccameras and similar apparatus in which one of two rollers is journalledat each end in a support plate while the other of the two rollers isjournalled at each end in a movable, spring-loaded bearing blockslidable in the support plate. The method involves a two-shot moldingtechnique by which the slidable bearing block is molded in place usingthe sliding guide surfaces of the support plate as a partial moldcavity.

In a commonly assigned U.S. Pat. No. 4,253,757 issued Mar. 3, 1981 toHarvey S. Friedman and Leon Rubinstein, there is disclosed a spreadroller assembly which is of a general class of such assemblies to theextent that it includes a pair of juxtaposed rollers adapted to beincorporated in the access door housing of a photographic camera andoperative for spreading a processing fluid across a layer on an exposedfilm unit to initiate the formation of a visible photographic image inthe film unit. In the patent disclosure, opposite ends of one of the tworollers, specifically the top roller, are journalled directly in aplate-like support member of molded plastic material. The molded supportmember is shaped to facilitate connection directly to the access doorhousing by snap fit, to provide a pivotal mounting of the access doorhousing from the camera body and to support various related componentssuch as a door latch and the like. The bottom roller is journalled ateach end in a movable bearing block also formed of molded plasticmaterial and adapted to be assembled with and slidably received in thesupport member for relative vertical movement. The movable bearingblocks are each biased upwardly by a coil spring acting between it andthe support member. The movable bearing block is further configured todefine a forwardly curved film engaging formation which though moved outof physical engagement with the film unit passing through the rollers asa result of downward displacement of the bottom roller by the thicknessof the film unit, moves upwardly to engage the film unit as the trailingend thereof exits from the nip of the two rollers.

The spread roller support arrangement disclosed in the aforementionedpatent has been demonstrated to be advantageous not only from thestandpoint of providing improved spread roller performance in processingfilm units exposed in instant cameras as compared with priorarrangements, but more significantly from the standpoint of greatlyreduced material and manufacturing costs. In this latter respect, theformation of the plate-like support members and movable bearing blocksfrom molded plastics and the facility provided for the use of simplelow-cost coil springs to develop the needed nip pressure between therollers result in important cost savings by comparison to priorextensive use of stamped metal for both the roller supports and inspecially fabricated leaf springs. Nevertheless, the requirement forassembly of individually formed parts remains as an increment ofmanufacturing cost of substantial magnitude in light of the largenumbers of spread roller assemblies used in the instant camera art.Accordingly, there is need for improvement in spread roller assembliesof the type disclosed in the aforementioned patent, particularly inreducing the time required for the assembly of each unit.

SUMMARY OF THE INVENTION

In accordance with the present invention, the assembly of a support anda slide carried by and for translational movement relative to thesupport, the support and slide corresponding respectively to theplate-like support member and movable bearing block of the rollersupport in a spread roller assembly of the type mentioned, is formed byinjecting a first plastic material into a mold cavity to form thesupport in a configuration defining a slide opening having opposed sideand end edges, respectively, and a pair of guides extending along theside edges from one of the end edges and diverging in the direction ofthe other of the end edges. The support is then enclosed in a moldshaped to complement the support and also to define with at least theguides and one of the end edges of the slide opening, a second moldcavity having a length less than the distance between the end edges ofthe slide opening. A second plastic material is then injected into thesecond mold cavity to form the slide. The first plastic material fromwhich the support is formed is preferably a glass filled polyesterhaving a relatively high melting temperature, for example 500° F.,whereas the second plastic material is preferably a glass filled acetalhaving a lower melting temperature, for example 400° F. By injecting thepolyester at temperatures at or only slightly above its melting pressurebut under relatively high injection pressures, solidification of theinjected material in the first mold occurs substantially instantaneouslyso that the first and second molding operations can be carried out inrapid succession. By injecting the acetal at a temperature substantiallyabove its melting point and at low injection pressures, distortion inthe preformed support is minimized. Additionally, provision is made formold reinforcement of the preformed support to minimize further anydeformation that may occur upon injecting the second plastic material toform the slide.

In the resulting roller support assembly, the guides of the opening inthe support member are defined as trapezoidal rails having a basesmaller than the thickness of the side edges of the opening and resultin complementary grooves along the side edges of the slides. The rate atwhich the guide rails diverge is correlated to the depth thereof so thatthe innermost edges of the guide rails are spaced less than the maximumdistance between the slide opening edges. The divergence of the railsinsures a parting of the slide from the guide rails in which it wasmolded and facilitates subsequent translational movement of the slidewithin the opening.

To facilitate formation of a forwardly curved film engaging formationdirectly on the slide, the support is configured to define a planar moldsurface at right angles to the edges of the slide opening. Also, theslide end supports are formed with spring receiving formations in thenature of recesses which, in the molding process facilitate mold gatingso that the second plastic is injected to engage steel mold surfacesprior to coming in contact with surfaces of the previously formedsupport.

Among the objects of the present invention, therefore, are the provisionof an improved method for molding the assembly of a support and a slideof general application; the provision of such a method for making theroller support subassembly of a spread roller assembly used in instantcameras; and the provision of an improved roller support subassembly forsuch spread roller assemblies which facilitates low-cost manufactureusing the method of the invention.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description to followtaken in conjunction with the accompanying drawings in which like partsare designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the working components of aspread roller assembly for use in instant cameras and the like;

FIG. 2 is an exploded fragmentary perspective view illustrating one endof the assembly shown in FIG. 1;

FIG. 3 is an exploded fragmentary perspective view illustrating moldfragments for forming the slide of the present invention;

FIG. 4 is a fragmentary side elevation illustrating one side of theroller support shown in FIG. 2 with components positioned as formed;

FIG. 5 is a fragmentary side elevation showing the components of FIG. 4in a working inter-relationship;

FIGS. 6 and 7 are enlarged fragmentary cross-sections on lines 6--6 and7--7 of FIGS. 4 and 5, respectively;

FIG. 8 is a side elevation illustrating one side of a support plate ofthe invention;

FIG. 9 is a side elevation showing the opposite side of the plateillustrated in FIG. 8;

FIG. 10 is a front elevation illustrating a sliding bearing block of theinvention;

FIG. 11 is a side view of the bearing block shown in FIG. 10;

FIG. 12 is a bottom plan view of the bearing block shown in FIG. 10;

FIG. 13 is an enlarged fragmentary cross-section on line 13--13 of FIG.8;

FIG. 14 is an enlarged cross-section on line 14--14 of FIG. 8 andillustrating fragments of mold components by which the parts shown inFIGS. 8-12 are formed; and

FIG. 15 is an enlarged fragmentary cross-section similar to FIG. 14 buton line 15--15 of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 of the drawings, the major working components of a spreadroller assembly of the type used in instant cameras to process exposedfilm units and eject them from the body of such a camera include a pairof juxtaposed elongated rollers 10 and 12 rotatably carried at oppositeends by support assemblies 14 and 16. As described fully in theaforementioned U.S. Pat. No. 4,253,757, the components illustrated inFIG. 1 are adapted to be mounted in a film chamber access door housing(not shown) which is pivotal from the camera housing (also not shown) onan axis defined by a pair of aligned apertures 18 formed in rearwardlyand downwardly extending arms 20 and 22 on each of the supportassemblies 14 and 16, respectively. Also as described in theaforementioned U.S. patent, each of the rollers 10 and 12 are formed,respectively, with journal shafts 24 and 26 at opposite ends. As shownmost clearly in FIG. 2, the journal shaft 24 of the top roller 10extends through a bearing aperture 28 to be coupled at its outer endwith a double spur gear 30. The journal shaft 26 on the bottom roller 12extends through a similar bearing aperture 32 to be connected with arelatively small pinion gear 34 which meshes with the double gear sothat as the latter is driven by a gear train (not shown), both rollers10 and 12 will be rotated in opposite directions of rotation in theperformance of their film processing function. The ends of the rollers10 and 12 opposite from that shown in FIG. 2 are similarly journalled inthe support assembly 16 but without the gears 30 and 34 which areprovided at only one end of the rollers.

Because the spread roller assembly including the components shown inFIG. 1 may be characterized as having a "gear side" and a "non-gearside" and because the support assemblies 14 and 16 differ from eachother only in the sense that the support assembly 14 is designed tocooperate with additional components not related to the support of therollers 10 and 12, the support assemblies 14 and 16 will be referred tohereinafter as the "gear side" support assembly and the "non-gear side"support assembly, respectively.

The support assemblies 14 and 16 include, respectively, a plate-likesupport member 36 and 38 in which the bearing apertures 28 forsupporting the top roller are located, and a slide or slidable bearingblocks 40 and 41 in which the bearing apertures 32 for supporting thebottom roller 12 are located. Each of the support members or plates 36and 38 are formed with a slide opening or window 42 (FIG. 2) and 43(FIG. 8) in which the bearing blocks 40 and 41 are respectively slidablymounted in a manner to be described in detail below. Also, therespective bearing blocks 40 and 41 are biased upwardly in each supportassembly by coil springs 44 and 46 to develop nip pressure between therollers 10 and 12. The support assembly 14 additionally carries a latch48 having a slotted pivot aperture 50 adapted to be received over apivot lug 52 formed in the support member 36. A bow-shaped latch spring54 is engaged at opposite ends between a tang 56 on the latch 48 and alug 58 projecting from the outboard side of the support member 36. Thelatch 48 and the bow spring 54 are well known in the art and thoughdiffering in structure from the latch structure illustrated in theaforementioned U.S. Pat. No. 4,253,757 are disclosed in other U.S.patents including those referred to in the specification of that patent.From the standpoint of the present invention, therefore, such componentsas the latch 48 and the bow spring 54 are shown only to identifystructure included in the support assembly 14 for accommodating thelatch of the door housing (not shown) in which the complete assemblyshown in FIG. 1 is used. Also it will be noted in this respect, that thepivot lug 52 on the support member 36 is located in a recessed flat 60defined at its front edge by vertical flange 62 which functions at astop to limit opening or counterclockwise movement of the latch againstthe bias of the spring 54. A projecting stop lug 64 is positioned on thesupport member 36 to be engaged by an arm 66 on the latch 48 and thuslimit pivotal movement of the latch in a clockwise direction or in thedirection of pivotal bias by the bow spring 54.

The opposite side of the support plate 36 from the side visible in FIG.2, or the inboard side of the support plate 36, is a mirror image of theinboard side of the support member or plate 38 on the non-gear side ofthe support assembly 16. The inboard side of the support plate 38 isshown most clearly in FIG. 8 to include a rectangular boss 68 (above theslide window 43) through which the bearing aperture 28 opens. A springmounting boss formation 70 is located at the bottom of the window 43. Inthis context and as shown most clearly in FIG. 2, each of the springs 44and 46 includes two axially spaced coils 72 joined at their inner endsby a central bight-shaped leg 74 and ending at their outer ends as apair of L-shaped legs 76. As shown in phantom lines in FIG. 8, the bossformation 70 defines a pair of undercut recesses 78 for receiving theends of the L-shaped legs 76 of the springs, in this instance of thespring 46. The bight-shaped central legs 74 are stressed to engage thebottom of the bearing blocks 40 and 41 in a manner described in theaforementioned U.S. Pat. No. 4,253,757. Also as disclosed in thatpatent, a cantilevered latch spring 80 is included on the bottom of bothplates 36 and 38 for retention of the assemblies 14 and 16 in the accessdoor housing (not shown).

In addition to the aforementioned functioning formations presented onthe inboard sides of each of the support plates 36 and 38, a pair ofgenerally rectangular, vertically oriented mold retention recesses 82and 84 are spaced from the edges of the slide window 43. The retentionrecess 84 is foreshortened at its lower end by an arc-shaped projection86 which defines a mold flat 88 adjacent the window 43 and spacedinwardly from the general plane of the support plate inboard surface(see FIG. 13) for reasons which will be made apparent in the descriptionto follow below.

The outboard side of the support plate 38 of the non-gear side of theassembly 16 differs from the outboard surface of the support plate 36principally in the omission of formations needed in the plate 36 toaccommodate the latch 48 and spring 54. Thus as shown in FIGS. 9 and 13,the outboard surface of the plate 38 of the present invention ischaracterized as including an additional pair of rectangular, verticallyoriented mold retention recesses 90 and 92. Although the comparableoutboard surface of the support plate 36 on the gear-side of the supportassembly 14 differs slightly from that shown in FIG. 9, it will be notedthat a mold retention recess 94 (FIG. 2) is provided on the oppositeside of the slide window 42 from the stop flange 62.

The configuration of the slide windows 42 and 43 and related structuralformations by which the bearing blocks 40 and 41 are retained thereinmay be understood by reference to FIGS. 4-7 of the drawings. As shown inthese figures, each of the windows 42 and 43 is of a trapezoidalconfiguration to define a pair of parallel end edges 96 and 98 and apair of linear side edges 100 and 102 which diverge in a directionproceeding from the end edge 98 toward the end edge 96. In theillustrated embodiment, the divergence of the side edges 100 and 102 isachieved by an inclination in the side edge 100 at an angle Aperpendicular to both end edges 96 and 98. The opposite side edge 102 inthe illustrated embodiment is perpendicular to both end edges 96 and 98.It is contemplated, however, that either or both of the side edges 100and 102 may be inclined with respect to the other to achieve thedivergence of the side edges proceeding from the bottom end edge 98 tothe top end edge 96.

To provide suitable clearance, the angle of divergence, angle A, ismade, for example, 11/2° to provide 0.003 inch clearance when the 0.350inch long slide is moved to its working position adjoining the wide endof the opening. Hence, it should be understood that the width of theslide is made a very close fit, or that is, substantially equal in widthto the width of the opening adjoining the narrow end of the latter.Then, in accordance with the angle A, when the slide is movedapproximately 0.110 inch to its working position, proper clearanceresults.

Extending along each side edge 100 and 102 of the windows 42 and 43 is aguide rail 104 and 106, respectively, of trapezoidal cross-section todefine a relatively narrow rail end surface 108 spaced from the base ofthe rail at the respective window side edges by converging rail sidesurfaces 110. The rails 104 and 106 extend from the short end edge 98 ofeach window upwardly along the side surfaces 102 and 104 toapproximately 3/4 of the length of the window between the end edges 96and 98. Also it will be noted that the length of the rails 104 and 106is equal to the length or height of the sliding bearing blocks 40 and41.

In the preferred embodiment, the sides of the openings 42 and 43 carrythe rails 104 and 106 while the sides or bearing blocks 40 and 41 carrycomplementary grooves 124 and 126 as explained in detail below withregard to FIGS. 10-12. However, it should be understood that theposition of the rails and grooves can be reversed, and that the railsand grooves broadly define complementary side edge formations of theslide and opening.

The configuration of the sliding bearing blocks 40 and 41 presentidentical mirror images, the outboard side of the slidable block 40being shown in FIGS. 4 and 5 whereas the inboard side, front end andbottom of the sliding bearing block 41 on the non-gear assembly 16 areshown orthographically in FIGS. 10-12 of the drawings. Additionally, thecross-sectional illustrations in FIGS. 6 and 7 are applicable to bothslidable bearing blocks 40 and 41. As shown in FIGS. 10-12, the slidingblock 41 includes a plate-like body portion 112 in which the bearingaperture 32 is centrally located. The body portion 112 complementsprecisely the configuration of the slide windows 42 and 43 in thesupport plates 36 and 38 in the area of the window circumscribed by theend edge 98, the side edges 102, and a plane defining the top edges ofthe guide rails 106 and 108. As such, the body portion of each slidingbearing block 40 and 41 includes parallel top and bottom edges 114 and116 and a pair of side edges 118 and 120 which diverge at the angle A inthe direction proceeding from the bottom edge 116 to the top edge 114.Projecting from each side edge 118 and 120 are a pair of flanges 122 ofa configuration to define trapezoidal grooves 124 and 126 along therespective side edges 118 and 120. Because the grooves 124 and 126 areformed by the guide rails 104 and 106 in the slide windows 42 and 43 ina manner to be described below, they complement precisely the exteriorconfiguration of the guide rails.

Projecting from the inboard side of each of the sliding bearing blocks40 and 41 is a forwardly and upwardly inclined arcuate formation 128. Asshown in FIG. 10, the opposite surfaces 130 of the formation 128 whichproject from the inboard face of the body portion 112 converge outwardlyto provide mold draft. Also, an inner side surface 131 of the formation128 is spaced from the inboard surfaces of the body portion 112 as shownin FIGS. 11 and 12. A ridge-like surface 132 near the tip of theformation, however, is oriented in a precisely perpendicularrelationship to the inboard surface of the body 112 as well as to theaxis of the grooves 124 and 126. The formation 128 is provided as a filmengaging component of the spread roller assembly described in theaforementioned U.S. Pat. No. 4,253,757. The ridge 132, therefore, willlie parallel to the axis of the rollers 10 and 12 and also of the filmunit passed between those rollers.

As shown in FIG. 12, the formation 128 terminates at the bottom edge 116of the body portion 112 of the sliding bearing block 41 which includes acentral land 133 defined by a generally U-shaped spring receiving recess134 in the bottom of the body portion 112. As may be seen in FIG. 5, forexample, the central bight section of the spring is adapted to lie inthe recess 134 about the land formation 133.

The method of forming each of the support assemblies 14 and 16 isessentially the same, apart from specific mold cavity configurations,and will be described with reference to FIGS. 3 and 13-15 of thedrawings which illustrate mold fragments applicable to the region of theslide windows 42 and 43 in the respective support plates 36 and 38. Informing the non-gear side assembly 16, therefore, the plate member 38 isfirst molded by injecting a first plastic material into a first moldcavity which, though not illustrated in the drawings, will be of a shapeto define the shape of the plate member 38 as it is shown in FIGS. 8, 9,and 13, for example. The first plastic material used to form the plates36 and 38 is preferably a glass filled polyester having a meltingtemperature approximating 500° F. Examples of commercially availableresins which may be used for the first plastic material includepolyesters supplied by LNP Corporation, Malvern, Penna. under thedesignation WFL-4536 (a 30% glass filled polyester with 15%polytetrafluoroethylene and 2% silicon): WFL-4416 (a 30% glass filledpolyester with 2% silicon): and WFL-4418 (a 40% glass filled polyesterwith 2% silicon) and by Celenese Plastics Company of Chatham, N.J. a 30%glass filled polyester under the designation Celenex 3300. The Teflonand silicon content of such polyesters, where indicated, are desirablefor lubricating characteristics whereas the glass fill is provided forstrength and reduced molding shrinkage.

During injection of the first plastic or polyester, the temperature iscontrolled to provide a very small differential between the injectiontemperature and the melting temperature of the polyester. High moldingpressures on the order of 15,000 psi are used. The combination of thesmall temperature differential and the high injection pressurescontribute to the formation of a strong, shrinkage resistant plate whichsolidifies substantially instantaneously on mold cavity filling.

The plate member thus formed is then enclosed in a multi-part steelmold, exemplary parts of which are designated in the drawings by thereference numerals 136 and 138. As may be seen in FIGS. 3, 14 and 15,the mold parts 136 and 138 define with the side edges 100 and 102 andbottom edge 98 of the slide window 43 as well as the flat 88 on thearcuate projection 86, a second mold cavity defining the configurationof the sliding bearing block 41. As may be seen in FIG. 3, the mold part138 is provided with a rectangular die formation 142 adapted to fill theslide window 43 above the guide rails 104 and 106. In addition, the moldpart 138 includes a pair of ribs 144 and 146 as well as a U-shaped dieformation 148 located to define the spring cavity 134 at the bottom ofthe sliding bearing block 41. The rib formations 144 and 146 registerwith the rectangular recesses 90 and 92 on the outboard side of theplate member 38. The mold part 136 is similarly formed with ribformations 150 and 152 (FIG. 14) to engage in the rectangular recesses82 and 84 on the inboard side of the plate 38. In this way, theperipheral edges of the window 43 will be positively seized and retainedby the steel mold part 136 and 138. It is noted further in this respectthat in molding the gear side support assembly 14, the flange 62 andcomplementing mold cavity (not shown) serves a window retainingfunction. Similarly, the flange formations at the bottom edge of eachwindow prevent distortion in that region.

As may be seen in FIGS. 3 and 15, the second mold cavity 140 is gated inthe mold part 136 by a mold gate 154 located so that as a second plasticmaterial is injected into the cavity 140, it passes between the legs ofthe U-shaped die formation 148 on first entering the cavity 140. Bygating the second mold cavity in this way, the second plastic materialfirst contacts the steel formation 148 which operates as a heat sink tocool the second plastic during injection into the mold cavity 140. Inaddition, such a gating arrangement avoids direct impingement of thesecond plastic against the surfaces of the previously molded platemember 38.

The second plastic material is preferably a glass filled acetal having amelting temperature of approximately 400° F. Acetals availablecommercially and which are acceptable for the sliding bearing blocksinclude KFL-4536 (a 30% glass filled acetal having 15%polytetrafluoroethylene and 2% silicon) and KFL-4416 (a 30% glass filledacetal having a 2% silicon content), both of which are available fromLNP Corporation; Celcon GC-25 (a 25% glass coupled acetal) from CelenesePlastics Company; and Delrin, 500 CL (a 20% glass filled acetal)available from E. I. Dupont Company.

The second plastic is injected into the mold cavity 140 at a moldingtemperature having a larger temperature differential relative to themelting temperature of the second plastic. For example, if the meltingtemperature of the acetal is 400° F., it is injected at a temperature ofapproximately 410° F. to 415° F. Also the second plastic is injected atrelatively low injection pressures such as approximately 500 psi. As aresult of the injection temperature differential relative to the meltingtemperature of the acetal and the relatively low pressures, highershrinkage results on cooling of the second plastic than would occur if asmaller temperature differential were used. Also, because thetemperature of the second plastic is always lower than the first plasticmaterial, no damage to the first plastic material occurs.

The assembly of the slidable bearing blocks 40, 41 with the supportplates 36, 38 on removal of the assembly from the mold parts 136 and 138is as shown in FIGS. 4 and 6 of the drawings. Specifically, the bearingblock 40 is shown against the bottom edge 98 of the slide window 42 and,as shown in FIG. 6, the adjacent surfaces of the guide rails 104 and 106as well as the grooves 124 and 126 of the bearing block 40 are in firmcontact with each other. Because of the divergence of the side walls 100and 102 at the angle A, however, slight upward movement of the slide 40will result in a parting of the guide rail and guide groove surfaces.This condition is illustrated in FIG. 7 of the drawings. The angle A isselected in practice to be on the order of 1-3 degrees. This angle ofdivergence will allow for proper parting of the bearing block and theguide rails and will provide very smooth sliding movement of the bearingblock in the region of the working position thereof which is illustratedgenerally in FIG. 5. The arrangement allows a spring force ofapproximately 4.8 pounds and results in extremely low hysteresis lossesin movement of the slide during operation of the spread roller assembly.

Thus it will be seen that as a result of the present invention, anextremely effective support plate/slide assembly and method for itsmanufacture are provided by which the above mentioned objectives arecompletely fulfilled. Although the assembly is particularly intended foruse in the illustrated spread roller assembly, it will be appreciatedthat the basic assembly and its method of manufacture will haveapplication broadly to assemblies of the type in which a sliding memberis received in a support. Also it will be apparent to those skilled inthe art from the preceding description that modifications and/or changesmay be made in the described embodiments without departure from thepresent invention. Accordingly, it is expressly intended that theforegoing description and accompanying drawings are illustrative of apreferred embodiment only, not limiting, and that the true spirit andscope of the present invention be determined by reference to theappended claims.

I claim:
 1. The method of forming a slide bearing assembly of a supportand a slide bearing carried by the support for translational movementrelative thereto, said method comprising the steps of:injecting a firstplastic material into a first mold cavity to form a support defining aslide opening having opposed side edge formations and a pair of endedges, with said side edge formations diverging slightly as they extendaway from one end edge; enclosing said support in a mold which defines,with portions of said opening, a second mold cavity adjoining said oneend edge of said opening and having a length within said slide openingof less than the distance between said end edges of said opening;injecting a second plastic material into said second mold cavity to molda slide bearing within said slide opening adjoining its said one endedge with a pair of side edge formations complementing adjoiningportions of said side edge formations of said opening such that thewidth of said slide bearing is substantially equal to the width of saidopening adjoining its said one end edge; and advancing said slidebearing away from its molded position adjoining said one end edge to abearing position where a sliding clearance is provided in accordancewith the divergence of said side edge formations of said opening.
 2. Themethod recited in claim 1, wherein said first plastic material has amelting temperature higher than the melting temperature of said secondplastic material and wherein said first plastic material is injectedunder relatively high molding pressures at temperatures slightly inexcess of the first plastic material melting temperature, and saidsecond plastic material is injected under relatively low moldingpressures and at temperatures substantially above the meltingtemperature thereof but lower than the melting temperature of said firstplastic material.
 3. The method recited in claim 2, wherein said firstplastic material has a melting temperature on the order of 500° F. andis injected at pressures on the order of 15,000 psi, and said secondplastic material has a melting temperature on the order of 400° F. andis injected at pressures on the order of 500 psi.
 4. The method recitedin claim 3, wherein said first plastic material is a glass filledpolyester and said second plastic material is a glass filled acetal. 5.The method recited in claim 1, including the step of retaining the edgesof said slide opening by said mold during injection of said secondplastic material.
 6. The method recited in claim 1, wherein said molddefining said second cavity includes a U-shaped projection to define aspring recess at an edge of the slide and comprising the step of gatingsaid second mold cavity so that said second plastic material isintroduced thereinto against said U-shaped projection.
 7. The method ofclaim 1 wherein said slide bearing and at least a portion of said sideedge formations of said opening are formed as complementary guide railsand grooves which retain said slide within said opening.
 8. The methodof claim 1 wherein said support is formed with side edge formationscomprising rails projecting from bases along a portion of said sideedges of said opening and with each of said rails having guide surfacesconverging inwardly of said opening to a rail edge, and said slidebearing is molded within said opening with the side edge formation ofsaid slide forming grooves which complement said rails so as to retainsaid slide bearing within said opening.
 9. The method of forming aroller supporting subassembly for use in a film processing spread rollerassembly having two juxtaposed rollers with one of the rollers beingtranslatable with respect to the other and retained against the otherunder a yieldable bias to provide a roll nip pressure, said methodcomprising the steps of:injecting a first plastic material into a firstmold cavity to form a plate-like support member having a fixed bearingto rotatably support an end of said other of said rollers and a slidewindow spaced from said fixed bearing, said slide window defining a pairof linear edge guides diverging from a narrow end to a wide end of saidwindow; enclosing said support member in a mold which defines, withportions of said slide window, a second mold cavity adjoining said oneend of said slide window with a length within said slide window of lessthan the distance between said end edges of said slide window; injectinga second plastic material into said second mold cavity to mold aslidable bearing block, having a bearing to rotatably support an end ofsaid one of the rollers, within the narrow end portion of said windowwith a length shorter than the distance between the ends of said window,and with a pair of side edge formations complementing adjoining portionsof said linear guides such that the width of said bearing block issubstantially equal to the width of said window adjoining its narrowend; and advancing said bearing block from its molded position to abearing position adjoining said wide end of said window where a slidingclearance is provided in accordance with the divergence of said edgeguides.